<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>圆角边框</title>
</head>
<style>
    div {
        width: 300px;
        height: 150px;
        background-color: red;
        border-radius: 10px;
    }
</style>
<body>
<div></div>
</body>
</html>